Printers Meant to Make Rockets
bloomberg.com
bloomberg.com
It makes sense. Rocket engines are mostly a big single piece with lots of internal voids. The fuel is used as a coolant, so there are channels inside the engine bell and some other sections. It's mostly plumbing.
That's the kind of part where 3D printing is useful. Making a big object with internal plumbing out of multiple parts is a fabrication headache. NASA's engines have vast amounts of welding work in them. High-pressure joints are always a problem. Making something with few or no joints is just better. It still has to be inspected, but that's what industrial-sized CAT scanners are for.
(Most of the real-world problems in both rockets and nuclear power involve plumbing and welding.)
In other ways it doesn't (depending on the techniques). Things like metallurgical resistance, defect creation and tolerances
https://youtu.be/RnIvhlKT7SY?t=14s
But the problem isn't the shape of the bell at all. It's that the wall of the bell is not solid, but hollow, filled with plumbing.
http://heroicrelics.org/info/f-1/f-1-thrust-chamber.html
The fuel actually flows through the pipes and voids in the red-hot engine, where it absorbs the heat that would otherwise melt the engine. It then flows back up to be burned.
You'd need an endoscope, not a robot arm, to mill that out!
And neither an endoscope (obviously) nor a robot arm would likely be rigid enough to mill in these materials. Robot arms are typically only used when milling wood, plastic, or soft modeling materials. A CNC mill in metals like the exotic Nobium alloys used in these engines needs incredible rigidity which robot arms just don't have. Consider the hardened tool-steel shafts of the end mills used in the first video - and those are easily broken, while just cutting aluminum!
but maybe it's the coming towards end of subtractive manufacture.
That said, I'm not a rocket scientist.
It makes sense that building single use rockets is expensive, and with only one launch to amortize the construction cost, labor is a huge factor (materials in a rocket are pretty normal: a lot of carbon fiber, aluminum, titanium, etc). But with reusable rockets, you are bringing that cost way down. If you are able to launch and land 5 times on the same rocket, then effectively you've brought the cost of the rocket to 1/5th of what it used to be.
"a handful of the arms can work together to create the rocket’s entire body as a single piece"
Once you get into reusable rockets, I'm not sure that trying to 3d print the whole thing will turn out. Why? Because you need replaceable parts. You need to be able to tear down, inspect, and replace parts as each part of the rocket has a different lifetime. If you make the rocket as one giant piece, and use efficient methods (reduce weight, size, etc), that it would be much less serviceable over its lifetime.
"We want to get to 1,000 moving parts, fewer than a car."
This is why subassemblies of cars are so expensive, even if you only need to replace a small part of one assembly.
My gut feeling about 3D printing is that it just makes it worse. How do you inspect a welding line as long as a rocket's dry mass?
For a solid fueled rocket, you're right that pretty much you have one shot, and you can't turn it off if something goes wrong.
> My gut feeling about 3D printing is that it just makes it worse. How do you inspect a welding line as long as a rocket's dry mass?
In general, the way you do this is to move it lengthwise through an x-ray scanner, so you can inspect the full length by moving the rocket through. I'm not sure if 3d printing makes this easier (because there's not really welds, it's one piece) or harder (you have to be able to inspect the inside of something), but it is certainly tricky.
Wait, isn't the result basically just one giant, continuous weld?
PS - totally not an expert on 3d printers or materials or welding
I think modern technologies prevent seams forming at most of those points, but the potential (impurities, dirt, etc.) still remains so must be tested.
The printers are going to make the exact same rocket every time.
And you could anneal the rocket after, which would improve the strength.
Also spacex seems to be doing it with their Dragon engine. Is there another rocket part that undergoes more strain? (vocab cringe, not a materials scientist)
Chamber pressure is limited by the fuel injection pressure. The simplest, fastest response time way to provide the fuel pressure is to use a high pressure bottle of gas to push the fuel through. Since those are important features in a launch escape system, that's how superdracos work.
But... chamber pressure is directly correlated with efficiency, so a main engine uses an extremely powerful fuel pump to achieve higher pressures.
That fuel pump is itself, a rocket engine with a gas pressure fuel system like the superdracos.
A 3d printed rocket would be cheaper right from the start, so they wouldn't need to bother with repairs, they can print another module or whole rocket again. Even a 3d printed rocket is going to be made of parts that can be replaced, because I presume we can't print the whole thing in one piece.
I think the idea is to 3D print parts that are currently welded together. I don't see anywhere that they are planning to print as one piece anything that is ever disassembled with current practices.
I would agree that 3d printing smaller parts and putting them together by hand seems more reasonable, but I don't get the impression that is what they're doing (but it's hard to tell from the article).
This is what led me to that conclusion: "Ellis and Noone say a handful of the arms can work together to create the rocket’s entire body as a single piece, guided by custom software that monitors their speed and the metal’s integrity."
Entire body - single piece. I don't hear any talk of welding or putting it together (which would involve multiple pieces).
Also just as a point of reference, making the bodies or the fuel tank is actually the easier part. It's either metal or carbon fiber. What takes a long time is assembling complex engines, and getting the whole thing together (including wiring).
Custom cars seems like one direction that has a lot more volume.
Think about how expensive it was to replace the heat shield tiles on the shuttle. The shuttle was “reusable” but the repairs were hell.
That is Awesome! Seeing how the protoss warped in objects from another spot... I guess to them 3D printing is the precursor to that.
[1]http://wiki.teamliquid.net/commons/images/thumb/e/e4/Protoss...
...I'll show myself out.
1. Does 3D printing make sense for large projects like rockets, which will be used in extreme conditions? I thought it was more for prototypes.
2. How does this compare to SpaceX, which is attempting to reuse rockets? How important is this fixed cost if you use a rocket 100 times?
I speculate that the disadvantage is that a many extreme environments also have hard requirements on the microscopic material structure of the components - and that will also have to be managed at the extruder/nozzle (as well as in the temperature and pressure environment afterward). Getting the materials properties right is much more finicky than the mechanical scale printing. And might change when you change the mechanical design (e.g. do you is there more material on some corner - then that might cool slower, which might give you a microscopic weakness around the corner...). I think you'll need world class materials modeling to do that right - and you'll have to do all sorts of validation that produced parts are ok.
In comparison, the spaceX welding techniques have less to worry about - the weld itself as well as properties the change/arise around the weld - the rocket tube presumably already at it's designed material strength.
I think you can do a crappy jet engine out of boring sintered stainless steel (316L), barely. Particularly if you could throw in some basic stuff from McMaster-Carr (seals/bearings/etc.)
Impressive for such an impoverished nation.
http://www.38north.org/2017/08/melleman082517/
http://www.armscontrolwonk.com/archive/1203086/wound-filamen...
http://edition.cnn.com/2017/08/23/asia/north-korea-missile-p...
It's a bit annoying for pages like Youtube where you do want autoplay to work, so you have to move the timeline cursor a bit, but the upside is worth it.
Also available in Chrome, I hear.